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MicroRNA-129-5p shuttled by mesenchymal stem cell-derived extracellular vesicles alleviates intervertebral disc degeneration via blockade of LRG1-mediated p38 MAPK activation.

ABSTRACT: Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) have been reported to deliver exogenous microRNAs (miRNAs or miRs) to reduce the progression of intervertebral disc degeneration (IDD). The purpose of the current study was to investigate the therapeutic potential of MSC-derived EVs delivering miR-129-5p in IDD. First, miR-129-5p expression levels were quantified in nucleus pulposus (NP) tissues of IDD patients. An IL-1β-induced NP cell model with IDD was then established, and co-cultured with EVs derived from MSCs that had been transfected with miR-129-5p mimic or inhibitor to elucidate the effects of miR-129-5p on cell viability, apoptosis, and ECM degradation. In addition, RAW264.7 cells were treated with the conditioned medium (CM) of NP cells. Next, the expression patterns of polarization markers and those of inflammatory factors in macrophages were detected using flow cytometry and ELISA, respectively. Lastly, rat models of IDD were established to validate the in vitro findings. It was found that miR-129-5p was poorly-expressed in NP tissues following IDD. Delivery of miR-129-5p to NP cells by MSC-derived EVs brought about a decrease in NP cell apoptosis, ECM degradation and M1 polarization of macrophages. Moreover, miR-129-5p directly-targeted LRG1, which subsequently promoted the activation of p38 MAPK signaling pathway, thus polarizing macrophages toward the M1 phenotype. Furthermore, MSC-derived EVs transferring miR-129-5p relieved IDD via inhibition of the LRG1/p38 MAPK signaling in vivo. Altogether, our findings indicated that MSC-derived EVs carrying miR-129-5p confer protection against IDD by targeting LRG1 and suppressing the p38 MAPK signaling pathway, offering a novel theranostic marker in IDD.

SUBMITTER: Cui S

PROVIDER: S-EPMC8330460 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Degenerative disc disease is associated with increased expression of pro-inflammatory cytokines in the intervertebral disc (IVD). However, it is not completely clear how inflammation arises in the IVD and which cellular compartments are involved in this process. Recently, the endoplasmic reticulum (ER) has emerged as a possible modulator of inflammation in age-related disorders. In addition, ER stress has been associated with the microenvironment of degenerated IVDs. Therefore, the aim of this study was to analyze the effects of ER stress on inflammatory responses in degenerated human IVDs and associated molecular mechanisms. Gene expression of ER stress marker GRP78 and pro-inflammatory cytokines IL-6, IL-8, IL-1β, and TNF-α was analyzed in human surgical IVD samples (n = 51, Pfirrmann grade 2-5). The expression of GRP78 positively correlated with the degeneration grade in lumbar IVDs and IL-6, but not with IL-1β and TNF-α. Another set of human surgical IVD samples (n = 25) was used to prepare primary cell cultures. ER stress inducer thapsigargin (Tg, 100 and 500 nM) activated gene and protein expression of IL-6 and induced phosphorylation of p38 MAPK. Both inhibition of p38 MAPK by SB203580 (10 µM) and knockdown of ER stress effector CCAAT-enhancer-binding protein homologous protein (CHOP) reduced gene and protein expression of IL-6 in Tg-treated cells. Furthermore, the effects of an inflammatory microenvironment on ER stress were tested. TNF-α (5 and 10 ng/mL) did not activate ER stress, while IL-1β (5 and 10 ng/mL) activated gene and protein expression of GRP78, but did not influence [Ca2+]i flux and expression of CHOP, indicating that pro-inflammatory cytokines alone may not induce ER stress in vivo. This study showed that IL-6 release in the IVD can be initiated following ER stress and that ER stress mediates IL-6 release through p38 MAPK and CHOP. Therapeutic targeting of ER stress response may reduce the consequences of the harsh microenvironment in degenerated IVD.

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MicroRNA-129-5p shuttled by mesenchymal stem cell-derived extracellular vesicles alleviates intervertebral disc degeneration via blockade of LRG1-mediated p38 MAPK activation.

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